Torx question
 

I need to replace the solenoid on my 96 (4.3L 4wd 4dr) blazer and found it uses torx screws. I have a set of torx bits (male); and lining them up, the screws look to be about T-27 or so. I've wanted to get a set of torx sockets and this will be my excuse. But what specific torx size are the screw heads? Also, just tighten them or is there a torque specification on these screws?